Frequently Asked Questions

What is six sigma?

Six sigma is a highly disciplined approach used to reduce the process variations to the extent that the level of defects are drastically reduced to less than 3.4 per million process, product or service opportunities (DPMO). Six sigma is a powerful approach to achieve breakthrough improvements in manufacturing, engineering and business processes. The approach relies heavily on advanced statistical methods that complement the process and product knowledge to reduce variation in processes. It is new way of doing business that would eliminate the existing defects efficiently and would prevent defects from occurring.


What is sigma?

Sigma is a Greek letter that is used to describe variability. In statistical quality control, this means “standard deviation”.

Who is using six sigma approach?

The six sigma approach was first introduced and developed at Motorola in late 1980s. Later in the mid-nineties, it was adopted by General Electric and Allied Signal. According to Jack Welch CEO of GE “Six sigma is the most challenging and potentially rewarding strategy GE have ever undertaken” GE listed tremendous benefits of the approach in their annual report in 1997. Six Sigma is now adopted by many other reputed companies.

Why should we implement six sigma?

GE listed tremendous benefits of the approach in their annual report in 1997. These benefits included:

* 10 fold increase in the life of CT scanner x-ray tubes at Medical Devices

* Improved yield resulting in increased capacity without additional investments at Superabrasives- their industrial diamond business

* 62% reduction in turnaround time at the repair shops of the railcar leasing business

* Addition of 300 million pounds of new capacity This was equivalent to adding new plant!

Your company can also get similar benefits by implementing six sigma.

Who is a six sigma black belt?

Black belts are full time six sigma project leaders who are selected to execute the project. Selection of candidates is critical for the success. The project leaders go through in-depth training of six sigma approach and tools and work full time on the project. They are usually future leaders of the organization. Black belt projects can be from any function in the company Financial benefits of a black belt project may be about 100000 US $. However, this may vary considerably depending on the stage of six sigma implementation.


What are green belts?

Green belts also lead six sigma projects. But the complexity of the projects and the benefits are somewhat less than that of black belt projects. Green belts work part time on projects and the projects usually belong to their own function. The training could be less intensive as compared to black belts. Financial benefits of a green belt project may be about 20000 US $. How are six sigma projects selected? Six sigma projects are identified considering the:

* Strategic direction of the company

* Impact on the bottom-line

* Impact on customer satisfaction

The projects having large impact requires project leaders with high degree of competence. Full time project leaders, called black belts, are selected to execute the project. Selection of candidates is critical for the success. The project leaders go through in-depth training of six sigma approach and tools and work full time on the project. Projects are expected to be completed by the belts in about six months time. Black belts may work on more than one projects at a time.


What are project sponsors?

Each project has a sponsor who is adequately senior in the organization. Sponsor ensures that

* The belt gets appropriate support from functions

* Resources are available

* The progress is as per schedule

* Organizational blocks are removed

In general, the sponsor owns the project and is accountable for the success of the project. Six sigma projects are identified considering the What is the difference between statistical quality control (SQC) and six sigma? There are many tools that were known to statisticians including design of experiments. However, the usage of tools was very limited. Also, few quality professions used these. In six sigma approach, the tools are learned by black and green belts who belong to different functions and apply the tools to make improvements in business processes. Thus six sigma is a company-wide initiative while as SQC was primarily deployed for quality control.

What is duration of six sigma black belt training?

Black belt training duration is usually three to four weeks. However, belts go through one week training and apply the learnings for the project. Thus, there is one week training every month for three months. In addition to this, there is a short two days introductory training for belts as well as sponsors in the beginning.

What is the role of senior management?

Top management must be committed to six sigma implementation. This must be demonstrated through:

* Making high performers available as black and green belts for six sigma projects.

* Making resources available for training and implementation.

* Project successes are celebrated and belts and team members are recognized and rewarded appropriately. Their presence during recognition is a strong indicator. GE made six sigma implementation as a condition from promotion of their managers.

Some of the senior managers should take up and implement six sigma projects Can we implement Six sigma along with other improvement initiative such as TPM? There is no rule of thumb. However, many of the resources, such as members of steering committee, are common to these initiatives. More than one initiatives becomes highly taxing for senior and middle management. In the days of lean organizations, both initiatives may suffer due to inadequate resource availability. In terms of principles, usually there are no contradictions between various improvement initiatives such as TPM, Six Sigma or TQM.


Is there any training required for senior management?

Yes. This is executive overview if six sigma approach, benefits and roles of belts, sponsors and top management. Duration could be one to two days

Is there any black or green belt certification?

There could be internal or external certification. This is based on successful completion of training and project. One of the widely recognized external certifications is by American Society for Quality (ASQ). ASQ conducts examination of multiple choice questions periodically. Link to ASQ six sigma black belt certification:

How many black belts should we have?

There is no standard for this. However, a rule of thumb is one black belt per 100 employees. It is essential that the technology of the organization is considered to arrive at a critical mass of black belts. Where the industry is labor intensive, number of black belts can be less

How many years it will take to reach six sigma level?

Six sigma is an approach and achieving six sigma level in all measures of a company is still only a dream. It is possible to reach this level in some of the processes. Many companies that are considered good by us may be at 4 sigma level. Moving to five sigma level may take 3 to 5 years and will have a complete paradigm shift in the operations. Following table shows relation between sigma level and defects per million parts:                

Sigma Level PPM
2 308,537
3 66,807
4 6,210
5 233
6 3.4

We can see that improvement from 4 to 5 sigma level is more than 26 times! One sigma change in the operational measures mean a complete overhaul of the processes and may take a fairly long time. What level a company should target depends on the likely competition.

Do we need consultants to help implementation?

Usually yes. Implementation of six sigma relies heavily on extensive training to belts and sponsors. Consultants can also help implementation during the initial one or two cycles of projects.


What is a master black belt (MBB)?

A master black belt is very highly proficient in the six sigma tools and can train others in the methodology. Number of master black belts may be very few. 

Can six sigma be useful for improvements in service industry?

Six sigma was initially applied to improving manufacturing industry. However, in later years, companies have successfully applied six sigma to make improvements in service sectors such as Healthcare, Banking, Software, Education etc. Some of the powerful Six Sigma Tools were first used in Agriculture to improve yield. Thus Six Sigma Approach and Tools can be applied to virtually any industry.

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